The invention relates to a method of automatically verifying a signature of an individual and an apparatus for carrying out this method.
Signature verification is known for example from U.S. Pat. No. 4,495,644 (GB 2 104 698 A) in which a transducer pad is used for capturing the signature. The pressure caused by the individual's pen when signing on this transducer pad produces an analogue voltage which is converted to digital form. The digital values are processed under the control of a microprocessor to determine numerical parameter values each representing a significant feature of the signature. Examples of parameters are "Pen out of or in contact with paper", "Current and previous position of pen", "Pen down, pen up", "Length of signature", "Duration of signature", etc. The parameter values of a signature to be verified are then compared with the parameter values of a reference signature which were calculated and stored earlier. Depending on this comparison it is decided if the signature to be verified is true or false that means if the parameter values of the present signature match with the parameter values of the reference signature.
As a transducer pad is necessary for capturing the signature, the described system cannot be used in connection with signatures which were not written on this mechanical sensor. This has the consequence that the known system cannot verify signatures on cheques or the like which were signed away from the computer for example at home.
Furthermore, the parameters which can be calculated from the captured signature are not very expressive. For that reason, a lot of parameters are necessary to reach a high reliability for the TRUE/FALSE-decision and, as a consequence, the processor time and the need for storage is high.
An object of the invention is to provide a signature verification system which is able to verify any signature irrespective of where or when it was written.
Another object of the invention is to provide a signature verification system with increased reliability but with decreased processor requirements.